This paper investigates the phonetic specification of contour tones through a case study of the Mandarin rising tone. The patterns of variation in the realisation of the rising tone as a function of speech rate indicate that its specifications include targets pertaining to both the pitch movement and its end points: the slope of the F0 rise, the magnitude of the rise, and the alignment of the onset and offset of the rise. This analysis implies that the rising tone is overspecified, in that any one of the target properties can be derived from the other three (e.g. slope is predictable from the magnitude and timing of the rise). As a result, the targets conflict, and cannot all be realised. The conflict between tone targets is resolved by a compromise between them, a pattern that is analysed quantitatively by formulating the targets as weighted, violable constraints.